Tool and process for finishing a vehicle wheel surface

ABSTRACT

A vehicle wheel has an outboard face which includes a smoothed portion to provide a cosmetic finish to the wheel face. The smoothed portion is formed by pressing a cutting tool having a non-symmetrical tip against the wheel surface as the wheel is rotated.

BACKGROUND OF THE INVENTION

This invention relates in general to vehicle wheels and in particular toa vehicle wheel having an outboard face which includes a finishedportion to provide a cosmetically pleasing appearance to the wheel faceand a method and cutting tool for machining the finished portion of thewheel face to produce a smooth surface.

Vehicle wheels typically include an annular wheel rim and a circularwheel disc. The wheel disc can be formed across the outboard end of thewheel rim or recessed within the wheel rim. The wheel rim is adapted tocarry a pneumatically inflated tire. The wheel rim has inboard andoutboard tire retaining flanges formed on the ends thereof which extendin an outward radial direction to retain the tire on the wheel. Inboardand outboard tire bead seats are formed on the outer surface of thewheel rim adjacent to the corresponding tire retaining flange to supportthe tire wall beads and form an air-tight seal therewith. The wheel rimalso includes a reduced diameter deep well between the tire bead seatsto facilitate mounting the tire upon the wheel.

The wheel disc includes a central wheel hub for mounting the wheel upona vehicle. The inboard face of the wheel disc hub is typically machinedto form a flat surface to assure good contact between the wheel disc andthe vehicle wheel hub. A pilot hole and a plurality of wheel stud holesextend through the wheel hub. The pilot hole is centered on the hub andthe stud holes are spaced equally about a bolt hole circle which isconcentric with the pilot hole. The pilot hole can receive the end of anaxle while the wheel stud holes receive wheel studs for attaching thewheel to the vehicle. The wheel disc also typically includes a pluralityof wheel spokes which extend radially from the wheel hub to the wheelrim and support the hub within the rim.

Referring now to the drawings, a flow chart for a wheel manufacturingprocess is shown in FIG. 1. In functional block 10, a wheel is cast in asingle piece from a light weight metal such as aluminum, magnesium ortitanium, or an alloy of a light weight metal. Such wheels are becomingincreasingly popular because they weigh less than conventional steelwheels and can include outboard wheel disc faces which are formed in apleasing aesthetic shape. One piece wheel castings are usually formed bya gravity or low pressure casting process. The wheel castings arefinished by machining to a final shape.

Two separate machining stations are typically used to finish a wheelcasting. In functional block 11, the outboard end of a rough wheelcasting is clamped to the face of a first wheel lathe for a first set ofmachining operations. A wheel lathe is a dedicated machine designed tofinish wheels. Wheel lathes typically include a plurality of cuttingtools mounted upon a lathe turret. The turret is indexed to sequentiallymove each of the tools to the surface of the wheel casting. Wheel lathesare usually operated under Computer Numerical Control (CNC) tosequentially perform a number of related machining operations. Forexample, a wheel lathe turret can be equipped with a turning tool, afacing tool and a drill bit and the wheel lathe can be programmed tosequentially turn, face and bore a wheel casting. The wheel lathe facetypically includes a chuck having a plurality of jaws which grip theoutboard wheel retaining flange and tire bead seat. Consequently, theoutboard wheel rim end is not finished during the first set of machiningoperations.

The outside and inside surfaces of the wheel rim are turned to theirfinal shapes and the inboard surface of the wheel hub is faced infunctional block 12. Additionally, the inboard end of the wheel rim isfinished. The partially finished wheel casting is removed from the firstwheel lathe, reversed and clamped on a second wheel lathe for a secondset of machining operations in functional block 13. During the secondset of machining operations, the inboard wheel flange and tire bead seatare gripped in the jaws of the wheel lathe chuck, exposing the outboardsurface of the wheel disc and the outboard end of the wheel rim formachining.

In functional block 14, the second wheel lathe turns and faces theoutboard wheel face. During these operations, the outboard tireretaining flange and the outboard tire bead seat also are turned tofinal shapes. The surface of the hubcap retention area is machined tofinal shape and the stud mounting holes are drilled through the hub infunctional block 15. Alternately, the wheel casting may be removed fromthe wheel lathe and the drilling operation completed at another workstation.

During the facing and other machining operations, very fine grooves areformed in the surfaces of the wheel. Accordingly, the surface of thewheel is typically subjected to a finishing step, as shown in functionalblock 16. A typical finishing process involves polishing the wheelsurface to smooth the grooves and provide a lusterous appearance to thesurface of the wheel. The polishing is usually followed by applicationof a clear coating to protect the polished wheel surface.

A typical polishing operation is illustrated by a flow chart in FIG. 2.Polishing typically involves a first step of rough buffing with anabrasive compound as shown in functional block 20. The buffed wheel isdegreased in functional block 21. One frequently used method ofdegreasing involves passing the wheel through a chamber which is filledwith a solvent vapor. The solvent vapor condenses upon wheel, coveringthe entire wheel surface. Once the solvent has had a sufficient time todissolve any surface grease, the solvent is washed from the wheel tocomplete the degreasing. As shown in functional block 22, the wheel isthen wet polished with a liquid lubricant for the polishing abrasive.The wheel is usually rotated and rotating polishing wheels are appliedto the surface while a slurry of polishing abrasive and a carrier fluidis applied to the wheel surface. Next the wheel is rinsed in functionalblock 23. Typically, deionized water is used for the rinse.

The substances utilized during wheel polishing are generally toxic innature. Accordingly, it is common practice to ship the wheels to apolishing contractor who employs safety procedures to protect personnel.The contractor is also equipped to dispose of the toxic wastes generatedby the polishing operations.

The polished wheel surface is prepared for coating in functional block24. Typically, the preparation includes immersion of the wheel in achromate bath. Finally, a clear coating is applied to the wheel infunctional block 25. Usually, the clear coating is sprayed onto thewheel while the wheel is slowly rotated. The coating is then heated in acuring oven.

SUMMARY OF THE INVENTION

This invention relates to vehicle wheel having an outboard face whichincludes a finished portion to provide a cosmetically pleasingappearance to the wheel face and a method and improved cutting tool formachining the finished portion of the wheel face to produce a smoothsurface.

As described above, it is known to buff or polish a wheel surface.However, such processes require abrasives and solvents. Typical solventsinclude trichloroethylene, trichloroethane, sulfuric acid andperchloroethylene, which are toxic. Additionally, the lubricants for theabrasives can include animal lubricants such as grease and lard. Thepolishing wheels can produce air-borne lint during the polishing andbuffing operation. Accordingly, it is necessary to protect the workersfrom these materials and collect and dispose of the residues. Because ofthe complexity of the polishing operations and the need to appropriatelycontrol the environmental impact of the materials utilized, wheels areoften shipped to an outside contractor for polishing. This involvesadditional time and expense. Thus, it would be desirable to smooth thewheel face without polishing the wheel.

The present invention contemplates a vehicle wheel comprising an annularwheel rim portion and a wheel disc formed across the wheel rim. Thewheel disc has an outboard face which includes a smoothed portion toprovide a pleasing cosmetic appearance. It is further contemplated thatthe smoothed portion of the wheel disc face can extend over the entiresurface of the wheel disc outboard face. An optional protective coatingcan be formed over the smoothed portion of the wheel disc face.

The present invention further includes a process for forming adecorative surface upon a vehicle wheel face which comprises providing amachined vehicle wheel including a wheel rim and having a wheel discextending radially across the wheel rim. The machined wheel is mountedin a lathe. The wheel is rotated while an improved cutting tool having anon-symmetrical tip is urged against the outboard surface of the wheeldisc to smooth a portion of the wheel disc surface. The invention alsocontemplates smoothing the entire outboard face of the wheel disc.Subsequent to smoothing the wheel face, an optional protective coatingcan be applied to the smoothed surface.

Various objects and advantages of this invention will become apparent tothose skilled in the art from the following detailed description of thepreferred embodiment, when read in light of the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flow chart for a known process for manufacturing a one piecevehicle wheel.

FIG. 2 is a flow chart for a known process for polishing a one piecevehicle wheel.

FIG. 3 is a sectional view of a vehicle wheel and illustrates a processfor finishing the vehicle wheel face in accordance with the invention.

FIG. 4 is a plan view of a wheel surface finishing tool in accordancewith the invention that is used in the finishing process illustrated inFIG. 3.

FIG. 5 is a side elevation of the surface finishing tool shown in FIG.4.

FIG. 6 is an enlarged partial side elevation of the tool shown in FIG.5.

FIG. 7 is a flow chart for manufacturing a one piece vehicle wheel whichutilizes the surface finishing process illustrated in FIG. 3.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring again to the drawings, there is illustrated in FIG. 3, asectional view of a one piece wheel 30 having an outboard surface 31 anda process for finishing the wheel 30 in accordance with the presentinvention. The finishing involves cutting the wheel surface 31 with animproved cutting tool having a unique geometry that will be describedbelow. An increased brightness or shine of the wheel surface is expectedfrom the cutting process. Thus, the present invention is directed tosmoothing the visible portions of a wheel face to cosmetically improvethe appearance of the wheel face.

As shown in FIG. 3, the wheel 30 includes an annular wheel rim 32. Awheel disc 33 which includes the outboard surface 31 extends radiallyacross the outboard end of the wheel rim 32. The invention contemplatesmounting an inboard end of the wheel rim 32 in the jaws 34 of a lathe ora spinner chuck of a wheel lathe (not shown).

The wheel 30 is rotated about an axis 35, as shown by the arrow in FIG.3, by the wheel lathe. An improved cutting tool 40 is mounted upon atool holder 41 that is secured to a wheel lathe turret (not shown). Thewheel lathe urges the cutting tool 40 against the outboard wheel face 31to simultaneously remove material from the wheel face 31 and smooth thecut surface. The tool 40 is traversed in a radial direction from theoutboard end of the wheel rim 32 across the wheel face 31. The tool 40moves alternately toward and away from the center of the wheel disc 33,as shown by the small arrows in FIG. 3. As the tool 40 moves across thewheel face 31, the tool 40 also is moved axially to follow the contourof the wheel face 31. The invention further contemplates that theimproved cutting tool 40 can be inclined to smooth all possibleinclinations of the wheel face 31, such as horizontal, vertical orinclined, as illustrated in phantom in FIG. 3. Additionally, the tool 40can be advanced in an axial, or radial, direction to increase the amountof material removed from the wheel face 31. Liquid coolant is applied tothe working surface by a conventional supply means (not shown). As willbe described below, a portion of the surface of the wheel face 31 ismelted and then resolidified as the tool 40 passes thereover to form asmoothed portion of the wheel face 31.

As shown in FIGS. 4 and 5, the improved cutting tool 40 is a speciallymodified face cutting tool. The tool 40 has a rhombic shaped body 42having a bore 43 formed therethrough which receives a fastener (notshown) for securing the tool to the tool holder 41. The tool 40 isformed from a sintered carbide steel and includes a Poly CrystallineDiamond (PCD) insert 44 insert attached to one end. The insert 44includes an improved cutting tip 45 on one end that contacts the wheelface 31 and works the metal. The arrow in the upper left portion of FIG.4 indicates the direction of movement of the worked metal relative tothe cutting tool 40. The insert 44 has a length L of about six mm. Anmounting hole 45 formed through the tool 40 permits attachment of thetool 40 to the tool holder 41.

The present invention contemplates a special geometry for the cuttingtip 45. For comparison, a standard cutting tip is outlined by the dashedline labeled 46 in FIG. 4. While the standard cutting tip 46 issymmetrical about the centerline of the tool, the cutting tip 45 of theimproved tool 40 is non-symmetrical, having two different radii. Theleading edge of the tip 45 has a larger radius R₁ while the trailingedge of the tip 45 has a smaller radius R₂. Both radii R₁ and R₂ aretangent to the centerline of the tool 40. In the preferred embodiment,the leading edge radius R₁ is twice the trailing edge radius R₂.Additionally, the leading edge radius R₁ is selected to be greater thatthe rate of feed per revolution programmed into the wheel lathe to causemultiple cutting of the wheel surface prior to the tangent point of thetip 45. In the preferred embodiment, the leading edge radius R₁ is 3.01mm while the trailing edge radius R₂ is 1.5 mm. These radii compare to atypical standard cutting tip radius of 1.0 mm. The direction of movementof the wheel being worked is indicated by the arrow in FIG. 4.

As best seen in FIGS. 5 and 6, the insert 44 is canted at an angle αrelative to the top surface of the tool body 42. In the preferredembodiment, the angle α is seven degrees. A flat land 48 is formedaround the upper edge of the insert 44. The land 48 is perpendicular, orhas zero rake, to the top surface of the tool body 42. Because theinsert 44 is canted relative to the tool body 42, the cutting edge ofthe insert 44 also forms an angle of α with the tool body top surface.Thus, the cutting edge of the insert 44 is maintained tangent to thesurface of the face of the vehicle wheel. The land 48 has a width W thatis in the range of between 0.076 and 0.254 mm with the preferredembodiment having a width in the range of 0.076 to 0.127 mm. The lowerportion 49 of the insert 44 and the tool body 42 are undercut at anangle β to allow removal of the cut material. The angle β is in therange of five to 15 degrees and is five degrees in the preferredembodiment.

The tool holder 41 is of conventional design but is formed of anantivibration material, such as, for example, machinable carbide tominimize vibration by avoiding resonance. Also, the tool holder 41 isdesigned for a minimum extension from the wheel lathe turret to increasethe rigidity of the smear cutting tool 40. Additionally, it iscontemplated that the associated wheel lathe includes a balanced chuck,centering, locating and clamping mechanisms.

During operation, the zero rake land of the insert tip 44 rubs the wheelsurface causing “work hardening” of the wheel metal. This differs from aprocess commonly referred to as “smear cutting” where a tool is draggedin a “backward” direction over the workpiece to only smooth the surface.The present invention contemplates advancing the tool 40 in a “forward”direction. The unique geometry of the improved cutting tool tip 45simultaneously removes material from the wheel face and smooths thewheel face. The friction between the tool tip 45 and the wheel surfacegenerates sufficient heat to cause microscopic melting of the surfacemetal. The friction between the tool tip 45 and the wheel surface forcesa small amount of the melted metal in front of the tip 45 and into anysurface voids. The melted surface metal then resolidifies. The meltingand resolidification of the metal can leave a bright surface thatappears to have been polished.

The inventors believe that as a wheel solidifies following casting, alayer of oxidized metal is formed upon the surface of the wheel. Theoxidized layer is melted and quickly resolidifed during the cuttingprocess with the improved cutting tool 40. As a result, an oxidizedlayer does not have a chance to be formed. A similar process is utilizedto provide a lustrous surface finish to gold ingots. As a gold ingotsolidifies, the exterior surface becomes dull due to slight oxidation ofthe gold on the surface and impurities rising to the surface. A torch isused to heat and remelt the surface of the ingot to a semi-liquid state.The torch is quickly removed as soon as the ingot surface becomes shiny.This process for gold ingots is typically referred to as tinning. Theinventors have found that if the feedrate for the improved tool 40 isone tenth or less than the leading edge radius R₁, the surface appearsto have been polished. The finishing process also seals any pores thatcould allow air to escape from a pneumatic tire mounted upon the wheel.Accordingly, the inventors expect that the number of “leakers” will bereduced.

The invention further contemplates applying a protective coating (notshown) to the wheel disc face following the work hardening process. Theprotective coating covers the smoothed portion of the wheel and slowsthe surface oxidation process. Accordingly, the inventors expect thatthe wheel surface will retain its shiny appearance for a long time.However, it will be appreciated that such a protective coating isoptional. In the preferred embodiment, the protective coating is a clearcoating; however, other coatings can be applied to the smoothed surfaceportion [41].

The invention further contemplates a process for smoothing the wheelface that is illustrated by the flow chart shown in FIG. 7. Steps shownin FIG. 7 which are similar to steps shown in the flow charts in FIGS. 1and 2 and have the same numerical designators. In FIG. 7, a vehiclewheel is cast by a conventional casting process, such as, for example,gravity or low pressure casting, in functional block 10. In functionalblocks 11 through 15, the wheel casting is machined to a final shape asdescribed above.

In functional block 51, the outboard wheel face is smoothed on a wheellathe or other conventional wheel finishing machine. The wheel isrotated upon the wheel lathe while a cutting tool having the uniquegeometry described above is urged against and moved radially across theoutboard wheel face. Once the desired surface dimensions and finish havebeen achieved, the wheel is removed from the wheel lathe in functionalblock 52.

The wheel can then be finished with a surface preparation in functionalblock 25 followed by a coating and curing of the coating in functionalblock 25. As described above, application of the protective coating tothe smoothed wheel surface is optional. Thus, the present inventioncontemplates that smoothing is included as one of the steps in the priorart process for machining a wheel casting. For example, a cutting toolmounted upon a tool holder formed from an anti-vibration material can beadded to the turret of the wheel lathe used to machine the wheel castingand the smoothing operation included as one of the programmed machiningsteps for finishing the wheel casting. Alternately, a smoothing station,which is dedicated to smoothing the wheel faces, can be established atthe wheel manufacturing facility.

While the preferred embodiment has been described and illustrated aboveas smoothing the entire outboard wheel face, it will be appreciated thatonly a portion of the wheel face can be smoothed. For example, theesthetic design of the wheel may require that only a portion of thewheel face is to be lustrous with the remainder remaining as machined orpainted. Accordingly, only the portion which is desired to be lustrouswould be smoothed. Similarly, the invention also contemplates that theentire surface of wheel can be smoothed to provide an improvement in thecosmetic appearance to the wheel. Also, while the preferred embodimenthas been described as being applied to cast wheels, it will beappreciated that the cosmetic appearance of wheels formed by otherconventional processes also can be improved by smear cutting. Forexample, the present invention also contemplates smoothing the outboardsurface of forged or stamped wheel discs.

The inventors expect that using the improved cutting tool to cut andsmooth the wheel face to enhance the cosmetic appearance thereof willcost less than buffing or polishing of the wheel face. Also, because thewheel can be smoothed on existing wheel lathes, no capital cost forpolishing machines is required. The smoothing process eliminates boththe exposure of personnel to toxic substances utilized during polishingand the expense of disposing of the toxic wastes generated thereby.Production time and cost will also be reduced since the need to ship thewheel to a polishing contractor will be eliminated. The improved cuttingtool can extend into the wheel rim to reach the surface of a recessedwheel disc, which can be difficult to reach with polishing wheels. Thecutting and smoothing preserves crisp edge surfaces which may beaesthetically desirable. Such edges tend to be blunted or removed by theabrasive nature of the polishing process. While polishing tends tohighlight surface imperfections, cutting and smoothing tends to hidesuch surface imperfections.

In accordance with the provisions of the patent statutes, the principleand mode of operation of this invention have been explained andillustrated in its preferred embodiment. However, it must be understoodthat this invention may be practiced otherwise than as specificallyexplained and illustrated without departing from its spirit or scope.For example, while the preferred embodiment has been described for a onepiece vehicle wheel, it will be appreciated that the invention also canbe practiced upon two piece vehicle wheels having cast full face modularwheel discs. Also, the invention can be practiced upon a wheel spiderwhich is disposed within a wheel rim.

What is claimed is:
 1. A cutting tool for smoothing a wheel surfacecomprising: a rhombic shaped body portion having a mounting apertureformed therethrough; and a non-symmetrical insert carried upon one endof said body portion, said insert having arcuate leading and trailingedges, said leading edge having a leading edge radius and said trailingedge having a trailing edge radius, said leading edge radius beinggreater than the trailing edge radius, said insert also having a zerodegree land formed thereabout whereby the cutting edge of said insert ismaintained tangent to the wheel surface.
 2. A cutting tool according toclaim 1 wherein said insert is canted relative to a surface of said toolbody.
 3. A cutting tool according to claim 2 wherein said leading edgeradius is about three mm and said trailing edge radius is about 1.5 mm.4. A cutting tool according to claim 2 wherein said end of said bodyadjacent to said tip is undercut by an angle in the range of 5 to 15degrees.
 5. A cutting tool according to claim 4 wherein said undercut is5 degrees.
 6. A cutting tool according to claim 4 further including atool holder formed from an anti-vibration material.
 7. A cutting toolaccording to claim 1 wherein said insert is formed from a hardsubstance.
 8. A cutting tool according to claim 7 wherein said insert isformed from a poly crystalline diamond material.
 9. A cutting toolaccording to claim 8 wherein said leading edge radius is twice saidtrailing edge radius and further wherein said working tip has a zerodegree land formed thereabout.
 10. A cutting tool according to claim 9wherein said insert is canted relative to a surface of said tool body.11. A cutting tool according to claim 9 wherein said leading edge radiusis about three mm and said trailing edge radius is about 1.5 mm.
 12. Acutting tool according to claim 1 wherein said leading edge radius istwice said trailing edge radius.